Mixtures of 3-phenoxybenzyl chloride and 3-phenoxybenzal chloride are of interest for the preparation of insecticides: U.S. Pat. No. 4,014,940. It is highly desirable that such mixtures contain a minimum of ring-chlorinated by-products: not only do these by-products represent a loss of the desired products, but in the procedures shown in the patent, and in copending application Ser. No. 762,541 and now U.S. Pat. No. 4,085,147, by which a mixture of 3-phenoxybenzyl chloride and 3-phenoxybenzal chloride is converted to the insecticide, any ring-substituted by-product therein, or by-product(s) derived therefrom, will appear as undesirable contaminant(s) in the insecticide. Once formed, such ring-substituted by-products are very difficult to separate from the mixtures of the benzyl-and benzal chlorides, because of the similarities of their properties to those of the desired products.
Further, unreacted 3-phenoxytoluene also presents similar problems.
It is accordingly desirable to have available a method for converting 3-phenoxytoluene to mixtures of 3-phenoxybenzyl chloride and 3-phenoxybenzal chloride selectively in as high yield as possible.
It has now been found that such results can be attained by treating 3-phenoxytoluene with sulfuryl chloride, in the presence of a free-radical initiator, in a certain manner, under certain conditions.